Problem: Solve for $x$, $- \dfrac{x + 9}{5x - 4} = 4$
Solution: Multiply both sides of the equation by $5x - 4$ $ -(x + 9) = 4(5x - 4) $ $-x - 9 = 20x - 16$ $-9 = 21x - 16$ $7 = 21x$ $21x = 7$ $x = \dfrac{7}{21}$ Simplify. $x = \dfrac{1}{3}$